scholarly journals Analysis of cylindrical tunnels under combined primary near-fault seismic excitations and subsequent reverse fault rupture

2016 ◽  
pp. 5-26 ◽  
Author(s):  
Mahsa Gharizade Varnusfaderani
Keyword(s):  
Reverse Fault ◽  
Fault Rupture ◽  
Seismic Excitations ◽  
Near Fault

Near-Fault Monitoring Reveals Combined Seismic and Slow Activation of a Fault Branch within the Istanbul–Marmara Seismic Gap in Northwest Turkey

2021 ◽  
Author(s):  
Patricia Martínez-Garzón ◽  
Virginie Durand ◽  
Stephan Bentz ◽  
Grzegorz Kwiatek ◽  
Georg Dresen ◽  
...  
Keyword(s):  
Seismic Gap ◽  
Marmara Region ◽  
Fault Rupture ◽  
Aseismic Slip ◽  
Near Fault ◽  
Fault Monitoring ◽  
Aftershock Sequences ◽  
Borehole Strainmeter ◽  
Seismic Moment Release ◽  
Fluid Diffusion

Abstract Various geophysical observations show that seismic and aseismic slip on a fault may occur concurrently. We analyze microseismicity recordings from a temporary near-fault seismic network and borehole strainmeter data from the eastern Marmara region in northwest Turkey to track seismic and aseismic deformation around the hypocentral region of an Mw 4.5 earthquake in 2018. A slow transient is observed that lasted about 30 days starting at the time of the Mw 4.5 event. We study about 1200 microseismic events that occurred during 417 days after the Mw 4.5 event around the mainshock fault rupture. The seismicity reveals a strong temporal clustering, including four episodic seismic sequences, each containing more than 30 events per day. Seismicity from the first two sequences displayed typical characteristics driven by aseismic slip and/or fluids, such as the activation of a broader region around the mainshock and swarm-like topology. The third and fourth sequences correspond to typical mainshock–aftershock sequences. These observations suggest that slow slip and potentially fluid diffusion along the fault plane could have controlled the seismicity during the initial 150 days following the Mw 4.5 event. In contrast, stress redistribution and breaking of remaining asperities may have caused the activity after the initial 150 days. Our observation from a newly installed combined dense seismic and borehole strainmeter network follows an earlier observation of a slow transient occurring in conjunction with enhanced local seismic moment release in the same region. This suggests a frequent interaction of seismic and aseismic slip in the Istanbul–Marmara seismic gap.

Numerical Modeling of Near Fault Seismic Ground Motion for Denali Fault

2021 ◽  
Vol 12 (2) ◽  
pp. 0-0
Keyword(s):  
Ground Motion ◽  
Peak Ground Acceleration ◽  
Numerical Study ◽  
Ground Motions ◽  
Numerical Results ◽  
Fault Rupture ◽  
Ground Acceleration ◽  
Denali Fault ◽  
Near Fault ◽  
Good Agreement

An effective earthquake (Mw 7.9) struck Alaska on 3 November, 2002. This earthquake ruptured 340 km along Susitna Glacier, Denali and Totschunda faults in central Alaska. The peak ground acceleration (PGA) was recorded about 0.32 g at station PS10, which was located 3 km from the fault rupture. The PGA would have recorded a high value, if more instruments had been installed in the region. A numerical study has been conducted to find out the possible ground motion record that could occur at maximum horizontal slip during the Denali earthquake. The current study overcomes the limitation of number of elements to model the Denali fault. These numerical results are compared with observed ground motions. It is observed that the ground motions obtained through numerical analysis are in good agreement with observed ground motions. From numerical results, it is observed that the possible expected PGA is 0.62 g at maximum horizontal slip of Denali fault.

Near-fault seismic monitoring reveals the long-lasting activation of a local fault in the Marmara region controlled by slow slip 

2021 ◽  
Author(s):  
Patricia Martínez-Garzón ◽  
Virginie Durand ◽  
Stephan Bentz ◽  
Taylan Turkmen ◽  
Grzegorz Kwiatek ◽  
...  
Keyword(s):  
Temporal Distribution ◽  
Marmara Region ◽  
Slow Slip ◽  
Fault Rupture ◽  
Aseismic Slip ◽  
Seismic Sequences ◽  
Near Fault ◽  
Aftershock Sequences ◽  
Nw Turkey ◽  
Different Characteristics

<p>Recent laboratory and field observations show that fault seismic and aseismic slip may occur concurrently. Here, we combine microseismicity recordings from a temporary near-fault seismic network (SMARTnet) and borehole strainmeter data from the eastern Marmara region in NW Turkey to track seismic and aseismic deformation around the hypocentral region of a M<sub>W</sub> 4.5 earthquake that occurred in 2018. The strainmeter data show a clear strain signal transient starting at the time of the M<sub>W</sub> 4.5 event and lasting for about 150 days. We study about 1,200 microseismic events following the mainshock within and beyond the mainshock fault rupture. The temporal distribution of the seismicity reveals a strong temporal clustering, including four semi-periodic seismic sequences each containing more than 50 events in two days. Two seismic sequences occurred during the strain transient showing different characteristics compared to two sequences occurring afterwards. Seismicity occurring during the transient displayed typical characteristics driven by aseismic slip, such as the activation of a broader region from the mainshock, and the absence of a clear mainshock in each sequence. Seismic sequences occurring after the transient correspond to typical mainshock-aftershock sequences and activated a region closer to the original M<sub>W</sub> 4.5 mainshock. We suggest post-strain transient seismicity originate from stress redistribution and breaking of remaining asperities. Our observations from a newly installed combined dense seismic and strainmeter network in the eastern Sea of Marmara region allows identifying repeated triggering of aseismic transients within an observation period of three years suggesting these may occur more often than previously thought.</p>

Seismic Performance of Guideway Sliding Isolator with Gap Springs for Precision Machinery

2008 ◽  
Vol 11 (5) ◽  
pp. 511-524
Author(s):  
George C. Yao ◽  
Wen-Chun Huang ◽  
Fan-Ru Lin
Keyword(s):  
Shaking Table Test ◽  
Model Simulation ◽  
Shaking Table ◽  
Viscous Damping ◽  
Far Field ◽  
Seismic Excitations ◽  
Isolation System ◽  
Near Fault ◽  
Seismic Motion ◽  
Nonlinear Performance

The performance of gap springs in a guideway sliding isolator (GSI) system developed to protect precision machinery against seismic motion has been studied. A spring is initially distanced from the system by a gap, causing the isolation system to exhibit nonlinear performance once the gap is closed, reducing the chance of resonance. A full-scale shaking table test of a 22-ton specimen and a numerical model simulation in SAP2000 have been performed. The study shows that springs possessing the appropriate gaps are more effective in controlling relative displacements than is a pure friction system. The optimal gap for a system subjected to far-field earthquakes was found to be 5mm. In addition, supplemental viscous damping of less than 15% of the critical damping had no significant effect on the GSI system far-field seismic response, but it did reduce the relative displacements of the system for near-fault seismic excitations.

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